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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Introduction to Physics

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Introduction to Physics

∫ dx 2ax - x^2 = a^n ^ -1 ((x)/(a) -1) . Determine the value of n ....

∫dx2ax−x2=ansin⁡−1(xa−1)\displaystyle \int \dfrac{dx}{\sqrt{2ax - x^2}} = a^n \sin^{-1} \left(\dfrac{x}{a} -1\right).
Determine the value of nn.
You may use dimensional analysis to solve the problem.$$

Options

  1. A00
  2. B−1-1
  3. C1/21/2
  4. D11

Correct answer

A. 00

Step-by-step solution

Let the dimension of xx be [L][L].

The dimension of dxdx is [L][L].

For the term 2ax−x22ax - x^2 to be dimensionally consistent, the dimension of aa must be [L][L].

The dimension of the denominator 2ax−x2\sqrt{2ax - x^2} is [L2]=[L]\sqrt{[L^2]} = [L].

Therefore, the dimension of the left-hand side is [L][L]=[L0]\dfrac{[L]}{[L]} = [L^0].

On the right-hand side, the argument of the inverse sine function, xa−1\dfrac{x}{a} - 1, is dimensionless. The function sin⁡−1\sin^{-1} yields an angle, which is also dimensionless.

Thus, the dimension of the right-hand side is [an]=[L]n[a^n] = [L]^n.

Equating the dimensions of both sides, we get [L0]=[L]n[L^0] = [L]^n, which implies n=0n = 0.

Alternatively, evaluating the integral directly:

∫dx2ax−x2=∫dxa2−(x2−2ax+a2)=∫dxa2−(x−a)2\int \dfrac{dx}{\sqrt{2ax - x^2}} = \int \dfrac{dx}{\sqrt{a^2 - (x^2 - 2ax + a^2)}} = \int \dfrac{dx}{\sqrt{a^2 - (x - a)^2}}

Using the standard formula ∫dxa2−x2=sin⁡−1\int \dfrac{dx}{\sqrt{a^2 - x^2}} = \sin^{-1}\left(\dfrac{x}{a}\right), we get:

\int \dfrac{dx}{\sqrt{a^2 - (x - a)^2}} = \sin^{-1} \left(\dfrac{x - a}{a}\right) = \sin^{-1}\left(\dfrac{x}{a} - 1\right)<br><br>Comparingthiswith<br><br>Comparing this witha^n \sin^{-1} \left(\dfrac{x}{a} -1\right),wefind, we finda^n = 1,whichgives, which givesn = 0..
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